Seven-Core Tapered Optical Fiber LSPR Biosensor With CMC Structure for Ultra-Sensitive Detection of Paraoxon in Environmental Monitoring

In this article, we introduce a seven-core tapered optical fiber biosensor with high sensitivity for label-free detection of paraoxon compounds that utilizes the localized surface plasmon resonance (LSPR) effect. By its unique circle-M-circle (CMC) structure surrounding the fiber surface, it achieves an obvious amplification of the evanescent field at the sensor and improves sensitivity greatly. Finally, the optimized tapered shape enhances surface plasmon light interaction and hence increases sensitivity to low concentrations of paraoxon residues. Since gold nanoparticles (AuNPs) are used as an active probe for surface modification, the optical properties of Au make them have a good LSPR effect. We also employ, as auxiliary materials, tungsten disulfide (WS2) thin layers and zinc oxide (ZnO) nanowires (NWs), of which the biocompatibility advantage can reinforce together with stability for detection probes to the WaveFlex sensor. The results of the experiment show a high sensitivity for detecting paraoxon residues in agricultural products: 33.8 ng/mL and a detection limit of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.83~\mu $ </tex-math></inline-formula>g/mL. The developed biosensor enables portability through miniaturization and also maintains its performance stability in various environmental conditions, which can be considered a powerful tool for field monitoring of paraoxon to enhance both environmental and food safety assessments. The sensor has shown favorable practical applicability due to at least desirable selectivity and repeatability. The CMC-like optical fiber-based WaveFlex biosensor being developed based on LSPR detection represents a great progress of sensor-based technology for environmental monitoring with wide application scenarios, which serves as an efficient and effective surveillance mechanism for point-of-sampling detection to the timely-onset paraoxon analysis.